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Hi, I'm Hillel. This is the newsletter version of [my website](https://www.hillelwayne.com). I post all website updates here. I also post weekly content just for the newsletter, on topics like * Formal Methods * Software History and Culture * Fringetech and exotic tooling * The philosophy and theory of software engineering You can see the archive of all public essays [here](https://buttondown.email/hillelwayne/archive/).

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Site URL: buttondown.com/hillelwayne

Feed URL: buttondown.com/hillelwayne/rss

Posts: 10

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Logic for Programmers extra credits

https://buttondown.com/hillelwayne/archive/logic-for-programmers-extra-credits/

Published: June 2, 2026 14:48

So I said there wasn’t a proper newsletter this week, since I’m in Budapest prepping for a conference. But I still got a thing for y’all. There’s a lot of interesting topics I wanted to cover for Logic for Programmers, but the book is dense enough as it is…

Assumptions weaken properties

https://buttondown.com/hillelwayne/archive/assumptions-weaken-properties/

Published: May 20, 2026 15:13

In some tests are stronger than others, I defined STRONG => WEAK to mean "any system passing test STRONG is also guaranteed to pass WEAK". This uses the logical implication operator, defined as P => Q = !P || (P && Q). Implication may be the most…

Points are a weird and inconsistent unit of measure

https://buttondown.com/hillelwayne/archive/points-are-a-weird-and-inconsistent-unit-of/

Published: May 13, 2026 15:56

I'm in the middle of redoing the Logic for Programmers diagrams and this has surfaced a really annoying problem. The book is formatted in LaTeX using a pseudo-grid of 10.8pt × 7.2pt. The diagrams are done in Inkscape using a 10.8pt × 7.2pt. Last week I…

Illegal vs Unwanted States

https://buttondown.com/hillelwayne/archive/illegal-vs-unwanted-states/

Published: April 28, 2026 15:14

An illegal state is a state we never want our system to be in. An unwanted state is a state we don't want to stay in. Many states that we wish were illegal are actually unwanted. Considering a calendaring software which stores calendar events as {user:…

People get confused when language implementations break language guarantees

https://buttondown.com/hillelwayne/archive/people-get-confused-when-language-implementations/

Published: April 21, 2026 17:40

Take the following Python program: # x = 1, y = 2 x = 0 y = x print([x, y]) It'll print [0, 0]. If we swapped the two assignments, it'd instead print [0, 1]. Each assignment happens in a separate temporal step. Pretty much all imperative languages behave…

A sufficiently comprehensive spec is not (necessarily) code

https://buttondown.com/hillelwayne/archive/a-sufficiently-comprehensive-spec-is-not/

Published: April 15, 2026 16:18

Sorry for missing last week! Was sick and then busy. This week I want to cover a pet peeve of mine, best seen in this comic: A "comprehensive and precise spec" is not necessarily code. A specification corresponds to a set of possible implementations, and…